使用硬度、条痕、光泽、解理、晶体形态和简单化学测试进行矿物和矿石的野外鉴定。 涵盖系统排除法、莫氏硬度标尺应用,以及贵金属、宝石和工业矿物的常见矿石指标。 适用于遇到未知岩石或矿物标本时、探矿评估场地是否显示有价值的矿物指标时、在 野外区分含矿岩石与贫矿岩石时,或通过系统观察建立地质素养时。
使用物理性质、系统排除法和简单的野外测试在野外鉴定矿物。
在拿取之前,在环境中观察标本。
Field Context:
+--------------------+------------------------------------------+
| Observation | Record |
+--------------------+------------------------------------------+
| Host rock | What type of rock is it in/on? |
| | (granite, basite, sandstone, schist...) |
+--------------------+------------------------------------------+
| Geological setting | Vein, disseminated, massive, placer, |
| | weathering surface, cave deposit |
+--------------------+------------------------------------------+
| Associated | What other minerals are nearby? |
| minerals | (quartz veins often host gold; iron |
| | staining suggests oxidation zone) |
+--------------------+------------------------------------------+
| Crystal form | Visible crystals? Habit? Size? |
| (if visible) | (cubic, prismatic, tabular, massive) |
+--------------------+------------------------------------------+
预期结果: 在拿取标本之前已记录野外环境。
失败处理: 如果地质环境不明确(散落标本、城市中发现),仅通过物理性质继续——环境本可帮助缩小候选范围但不是严格必需的。
系统地应用诊断测试。
Diagnostic Property Tests:
LUSTER (how it reflects light):
- Metallic: reflects like metal (pyrite, galena, gold)
- Vitreous: glassy (quartz, feldspar)
- Pearly: like a pearl (muscovite, talc surfaces)
- Silky: like silk fibers (asbestos, satin spar gypsum)
- Earthy/dull: no reflection (kaolin, limonite)
- Adamantine: brilliant, diamond-like (diamond, zircon)
HARDNESS (Mohs scale — scratch test):
+------+-----------+----------------------------------+
| Mohs | Reference | Can Be Scratched By |
+------+-----------+----------------------------------+
| 1 | Talc | Fingernail |
| 2 | Gypsum | Fingernail (barely) |
| 3 | Calcite | Copper coin |
| 4 | Fluorite | Steel nail (easily) |
| 5 | Apatite | Steel nail (just) |
| 6 | Feldspar | Steel nail cannot scratch |
| 7 | Quartz | Scratches glass |
| 8 | Topaz | Scratches quartz |
| 9 | Corundum | Scratches topaz |
| 10 | Diamond | Scratches everything |
+------+-----------+----------------------------------+
Test: try to scratch the specimen with each reference tool,
starting from soft to hard. The hardness is between the tool
that fails and the tool that succeeds.
STREAK (powder colour on porcelain):
- Drag the specimen firmly across an unglazed porcelain tile
- Record the colour of the powder line
- Streak colour is often different from specimen colour
- Critical: hematite is grey-black but streaks RED
- Critical: pyrite is gold but streaks BLACK
- Minerals harder than the streak plate (~7) will not leave a streak
CLEAVAGE AND FRACTURE:
- Cleavage: breaks along flat planes (mica: 1 direction, feldspar: 2)
- Fracture: breaks irregularly (conchoidal = curved like glass, uneven, fibrous)
- Note number of cleavage directions and angles between them
SPECIFIC GRAVITY (heft test):
- Hold the specimen and assess: does it feel heavier or lighter
than expected for its size?
- Heavy: possible metallic ore (galena, gold, magnetite)
- Light: possible pumice, sulfur, or organic material
预期结果: 标本的特征概要:光泽、硬度范围、条痕颜色、解理/断口类型和相对密度。
失败处理: 如果某个性质模棱两可(如光泽介于金属和玻璃之间——"亚金属"),记录两个选项。模棱两可降低可信度但不阻止鉴定。
针对特定矿物组的附加测试。
Special Field Tests:
MAGNETISM:
- Hold a magnet near the specimen
- Strong attraction: magnetite (or possibly pyrrhotite)
- Weak attraction: some iron-bearing minerals
ACID TEST (10% HCl):
- Drop acid on the specimen surface
- Vigorous fizzing: calcite (CaCO3)
- Fizzing on powder only: dolomite (scratch surface first, then apply acid)
- No fizzing: not a carbonate
TASTE (only for suspected halite):
- Salty taste: halite (NaCl)
- Do NOT taste unknown minerals generally — some are toxic
SMELL:
- Sulfur: rotten egg smell (sulfides when scratched)
- Clay: earthy "petrichor" smell when breathed on (clay minerals)
TENACITY:
- Brittle: shatters when struck (most silicates)
- Malleable: deforms without breaking (gold, copper, silver)
- Flexible: bends and stays (chlorite, some micas)
- Elastic: bends and springs back (muscovite mica)
预期结果: 进一步缩小鉴定范围的附加诊断数据。
失败处理: 如果特殊测试不可用(无磁铁、无酸),仅凭基本性质继续——它们对大多数常见矿物已经足够。
将性质概要与已知矿物交叉对照。
Common Mineral Identification Key (simplified):
METALLIC LUSTER:
- Black streak + hard (6+) + cubic crystals = PYRITE
- Black streak + soft (2.5) + heavy + cubic = GALENA
- Red-brown streak + hard (5-6) + heavy = HEMATITE
- Yellow streak + soft (1.5-2.5) + yellow = GOLD (if malleable)
or CHALCOPYRITE (if brittle, harder, green-black streak)
- Black streak + magnetic = MAGNETITE
NON-METALLIC, LIGHT-COLORED:
- Vitreous + hard (7) + conchoidal fracture = QUARTZ
- Vitreous + hard (6) + 2 cleavage planes = FELDSPAR
- Vitreous + soft (3) + fizzes in acid = CALCITE
- Pearly + very soft (1) + greasy feel = TALC
- Vitreous + soft (2) + 1 perfect cleavage = GYPSUM
NON-METALLIC, DARK-COLORED:
- Vitreous + hard (5-6) + 2 cleavage at ~90 degrees = PYROXENE
- Vitreous + hard (5-6) + 2 cleavage at ~60/120 degrees = AMPHIBOLE
- Vitreous + soft (2.5-3) + 1 perfect cleavage + flexible = BIOTITE (mica)
预期结果: 矿物鉴定结果或 2-3 个候选的简短列表,以及区分它们所需的鉴别测试。
失败处理: 如果标本不匹配任何常见矿物,它可能是岩石(矿物集合体)而非单一矿物,或者可能需要实验室分析(薄片、XRD)。
gold-washing — 冲积金回收使用矿物鉴定技能来解读溪流沉积物并评估含金砂砾